In a conventional W-CDMA wireless system, closed loop (closed loop) type transmission diversity is applied occasionally. For example, in transmission diversity disclosed in Patent Document 1 hereinafter described, phases (carrier phases) of reception signals from two transmission antennas of a wireless base station are detected in a wireless terminal such as a mobile station and an optimum reception state (diversity synthesis) is established in the wireless terminal based on a result of the detection. In more detail, phase controlling information (transmission antenna weight) for minimization (ideally to zero) of the phase difference between the two reception signals is produced and transmitted (fad back) as an FBI (Feedback Indicator) bit to the wireless base station so that the signal phases from the transmission antennas are adaptively controlled.
By adaptively controlling the signal phases from the two transmission antennas of the wireless base station using the FBI bit from the wireless terminal in this manner, a bit error arising from a drop of reception power by fading can be reduced.
However, as disclosed in the paragraphs 0024 and 0025 of Patent Document 1, since, if an error occurs with the FBI bit in the uplink, then the wireless base station carries out transmission using a carrier phase different from that expected by the wireless terminal, suitable phase control is not carried out and the error ratio increases.
Therefore, in the technique of Patent Document 1, the wireless terminal carries out, using a pilot symbol of a dedicated physical channel (DPCH: Dedicated Physical CHannel) of the downlink, antenna verification for estimating the transmission antenna weight (transmission carrier phase) in each slot of the DPCH. Particularly, since, in the wireless communication system of the W-CDMA method, transmission power control (TPC) is carried out normally so that the communication quality of the uplink becomes constant, while, as a result, also the FBI bit is mistaken in a fixed probability, a reception characteristic of the downlink can be enhanced by carrying out the antenna verification.
Also in the HSDPA, similarly as in the case described above, antenna verification of an HS-PDSCH (High Speed Physical Downlink Shared Channel) that is a shared channel of the downlink can be applied and carried out using a dedicated pilot symbol of an associated dedicated physical channel (Associated Dedicated Physical Channel: A-DPCH) of the downlink (for example, refer to Patent Document 1).
However, since, if the antenna verification of the HS-PDSCH is controlled with the dedicated pilot symbol of the A-DPCH, then the power of the A-DPCH is generally very low in comparison with that of the HS-PDSCH. Therefore, the error ratio of the FBI bit increases rather than the degradation ratio of the quality of the HS-PDSCH and the throughput characteristic degrades on the contrary because of the antenna verification. In the technique of the Patent Document 1, in order to eliminate such a problem as just described, the control of the antenna verification is not used during the HSDPA (a result of estimation of signal phases from two transmission antennas is not reflected).
Patent Document 1: Japanese Laid-open Patent Publication No. 2006-222937